There are a number of different MRI equipment designs commercially available and depending upon the precise application, these designs will differ substantially in their structures, as well as function in different ways.
For example, the present assignee has developed a number of different methods and apparatuses for performing magnetic resonance imaging (MRI) both in animals and humans. Assignee's International Patent Application Serial No. PCT/US2004/027532, filed Aug. 23, 2004, which is hereby incorporated by reference in its entirety, discloses a microstrip-based RF coil for use in an MRI apparatus constructed to perform human head imaging. The microstrip coil includes a cylindrical non-magnetic core module having an outer surface and a longitudinal axis, a cylindrical bore extending through the core module along the longitudinal axis and defining an inner surface; and a plurality of conductive strip lines. The strip lines extend parallel to the longitudinal axis on the outer surface of the core module. The coil also includes a pair of circuit boards carried at or near the ends of the core module. The coil is constructed such that one or more of the conductive strips are divided into conductive microstrip segments, with one or more tuning capacitors being bridged between two adjacent microstrip segmented sections of the conductive strip. The coil also includes a shield support cylinder that is disposed concentrically about the core module and is spaced therefrom to receive the tuning capacitors. The shield support cylinder supports a conductive segmented shield that is operatively connected to the conductive strips through tunable capacitors at a front and rear of the shield support cylinder.
Although MRI scans are ideal for diagnosing and evaluating a number of conditions, it does have a number of drawbacks and in particular, being subjected to an MRI scan can be a very uncomfortable and frightening experience for some. More specifically, one of the chief complaints about the MRI experience is that there are many claustrophobic people in the world and being in an MRI machine can be a very disconcerting experience for these type of people. Even people that are not normally claustrophobic can feel uncomfortable in the MRI equipment since the patient must enter into the tubular MRI device which can lead to a feeling of being in a dark tunnel. In addition, an MRI device makes a tremendous amount of noise during the scan. The noise sounds like a continual, rapid hammering and while patients can use earplugs or stereo equipment to muffle the noise, the noise in combination with the darkness and the closeness of the inner surface of the device to the face and body makes it a potentially stressful environment. The noise is due to the rising electrical current in the wires of the gradient magnets being opposed by the main magnetic field. Moreover, MRI scans require patients to hold very still for an extended period of time. MRI exams can range in length from 20 minutes or less or can be upward of 90 minutes or more. Even slight movement of the patient being scanned can cause very distorted images that will have to be repeated. The above characteristics of the MRI experience make it difficult for some patients and one of the biggest factor that patients mention when describing the MRI experience is that they feel uneasy and uncomfortable when their head is contained within a dark tubular structure and they are unable to see outside of the MRI device.
Performance of the MRI coil also suffers when the size of the coil does not conform well to the patients body. A coil design that is more ergonomic in nature will put the coil elements closer to the patient without closing in the patient. The closer the coil elements are to the patient, the more sensitive they are and the more signal they collect, resulting in shorter signal collection times. This reduces the patients time inside the MRI apparatus.